How can the interior surface of sealed structural steel tubing best be protected against corrosion?

The best approach to protect the interior surface of sealed structural steel tubing against corrosion is through methods that provide a lasting barrier against moisture and other corrosive elements. Applying a coating like linseed oil, while it might offer some initial protection, is not the most effective long-term solution. Linseed oil can become oxidized and degrade over time, which could compromise its effectiveness in preventing corrosion.

Using a paint designed for metals could be beneficial for external surfaces, as these paints typically include properties that resist corrosion. However, they may not adhere well to the interior environment of a sealed tube, where factors like humidity and limited ventilation come into play.

Sealing with a rubber gasket focuses on creating a barrier to moisture but does not actively protect against corrosion that can occur from moisture trapped inside the tubing itself.

Galvanized coatings, which involve applying a layer of zinc to the steel, provide excellent corrosion resistance and are commonly used for such applications because the zinc acts as a sacrificial anode; it will corrode before the underlying steel does. This method would be the optimal choice for protecting the interior surfaces of steel tubing from corrosion, making it the recommended solution.